64 COSMOS. 



they are small celestial bodies, which, being attracted by out 

 planet, are made to deviate from their original course, and thus 

 reach the earth enveloped in vapors, and in a high state of 

 actual incandescence. The familiar aspect of these asteroids, 

 and the analogies which they present with the minerals com- 

 posing the earth's crust, undoubtedly afford ample grounds for 

 surprise ;* but, in my opinion, the only conclusion to be drawn 

 from these facts is, that, in general, planets and other sidereal 

 masses, which, by the influence of a central body, have been 

 agglomerated into rings of vapor, and subsequently into sphe- 

 roids, being integrant parts of the same system, and having 

 one common origin, may likewise be composed of substances 

 chemically identical. Again, experiments with the pendulum, 

 particularly those prosecuted with such rare precision by Bes- 

 sel, confirm the Newtonian axiom, that bodies the most hete- 

 rogeneous in their nature (as water, gold, quartz, granular 

 limestone, and diflerent masses of aerolites) experience a per- 

 fectly similar degree of acceleration from the attraction of the 

 earth. To the experiments of the pendulum may be added 

 the proofs furnished by purely astronomical observations. The 

 almost perfect identity of the mass of Jupiter, deduced from the 

 influence exercised by this stupendous planet on its own satel- 

 lites, on Encke's comet of short period, and on the small planets 

 Vesta, Juno, Ceres, and Pallas, indicates with equal certain- 

 ty that within the limits of actual observation attraction is 

 determined solely by the quantity of matter. t 



This absence of any perceptible difierence in the nature of 

 matter, alike proved by direct observation and theoretical de- 

 ductions, imparts a high degree of simplicity to the mechanism 

 of the heavens. The immeasurable extent of the regions of 

 space being subjected to laws of motion alone, the sidereal 

 portion of the science of the Cosmos is based on the pure and 

 abundant source of mathematical astronomy, as is the terres- 

 trial portion on physics, chemistry, and organic morphology ; 

 but the domain of these three last-named sciences embraces 



* [The analysis of an aeroHte which fell a few years since in Mary 

 land. United States, and was examined by Professor Silliman, of New 

 Haven, Connecticut, gave the following results: Oxyd of iron, 24 ; ox- 

 yd of nickel, 1*25 ; silica, with earthy matter, 3*46 ; sulphur, a trace 

 =28-71. Dr. Mantell's Wonders of Geology, 1848, vol. i.. p. 51.]— 7V. 



t Poisson, Connaissances des Temps pour V Annee 1836, p. (j4-6(). 

 Bessel, Poggeudorf 's Annalen, bd. xxv., s. 417. Encke, Abhandhingen 

 der Berliner Academie (Trans, of the Berlin Academy), 1826, s. 257. 

 Mitscherlich, Lehrbuck der Chemie (Manual of Chemistry), 1837 bd. i. 

 8. 352. 



